Power Pro 4000-MR offers superior velocity and lot-to-lot uniformity. A spherical powder designed for magnum rifle calibers, the 4000-MR powder delivers improved velocity and density for easier metering. Because it's designed for specific cartridge and applications, it will allow reloaders to create a load similar to factory loaded ammunition. the 4000-MR powder offers superior performance for 7mm and 300 Winchester Magnum cartridges. 8 lb. bottle.